Omitrix

The Omytrix is a Watch like Alien device that is used in the Ben Ten Series/Alien Force/Ultimate Alien/Omniverse, by Ben Tennyson (the Main Character), it allows the user to transform into a varity of Aliens that are on it.

Bellas version of the omytrix not only allows her to transform into the Aliens seen in the Ben 10 series, but it also allows her transform into her favorite cartoon characters at will.

Purpose
created by Azmuth, the Omyrtrix was suposed to be used as a way for peace and understanding via in a way "to walk a mile in another persons shoes" but warlord and planitary conquer Vilgax wanted to use it to conquer the world, however it ended up on the wrist of Ben Tennyson who used it for good and to be a hero.

For Bella, it allowed her to fufill her dream of being able to transform into her favorite cartoon characters.

Bellas Omytrix
Bella's omytrix is unique to her as it allows her to transform into her favorite cartoon characters.